circopithican: of or relating to monkeys. For some reason I always remembered that from my Creative Writing teacher's dictionary of obscure words, though I don't think I've ever seen the word anywhere else including other dictionaries.
@kalbahamut: "House" will work now.
light being the answer for optic is as logical as speach being the answer to audio, yes you can hear it, but is not the origin of the word. And has nothing to do with the root.
Edit: if it was opticS you would have a point, that is used to refer to the science of sight AND light. But the word optic literally comes from to see...